Mutational analysis of the carboxy-terminal phosphorylation site of GLUT-4 in 3T3-L1 adipocytes

Marsh, B. J., Martin, S., Melvin, D. R., Martin, L. B., Alm, R. A., Gould, G. W. and James, D. E. (1998) Mutational analysis of the carboxy-terminal phosphorylation site of GLUT-4 in 3T3-L1 adipocytes. American Journal of Physiology-Endocrinology and Metabolism, 275 3: E412-E422.

Author Marsh, B. J.
Martin, S.
Melvin, D. R.
Martin, L. B.
Alm, R. A.
Gould, G. W.
James, D. E.
Title Mutational analysis of the carboxy-terminal phosphorylation site of GLUT-4 in 3T3-L1 adipocytes
Journal name American Journal of Physiology-Endocrinology and Metabolism   Check publisher's open access policy
ISSN 0193-1849
Publication date 1998-09
Sub-type Article (original research)
Volume 275
Issue 3
Start page E412
End page E422
Total pages 11
Language eng
Abstract The carboxy terminus of GLUT-4 contains a functional internalization motif (Leu-489Leu-490) that helps maintain its intracellular distribution in basal adipocytes. This motif is flanked by the major phosphorylation site in this protein (Ser-488), which may play a role in regulating GLUT-4 trafficking in adipocytes. In the present study, the targeting of GLUT-4 in which Ser-488 has been mutated to alanine (SAG) has been examined in stably transfected 3T3-L1 adipocytes. The trafficking of SAG was not significantly different from that of GLUT-4 in several respects. First, in the absence of insulin, the distribution of SAG was similar to GLUT-4 in that it was largely excluded from the cell surface and was enriched in small intracellular vesicles. Second, SAG exhibited insulin-dependent movement to the plasma membrane (4- to 5-fold) comparable to GLUT-4 (4- to 5-fold). Finally, okadaic acid, which has previously been shown to stimulate both GLUT-4 translocation and its phosphorylation at Ser-488, also stimulated the movement of SAG to the cell surface similarly to GLUT-4. Using immunoelectron microscopy, we have shown that GLUT-4 is localized to intracellular vesicles containing the Golgi-derived γ-adaptin subunit of AP-1 and that this localization is enhanced when Ser-488 is mutated to alanine. We conclude that the carboxy- terminal phosphorylation site in GLUT-4 (Ser-488) may play a role in intracellular sorting at the trans-Golgi network but does not play a major role in the regulated movement of GLUT-4 to the plasma membrane in 3T3-L1 adipocytes.
Keyword insulin action
translocation
endosome
Mannose 6-Phosphate Receptor
Regulatable Glucose Transporter
Insulin-Stimulated Glucose
Factor-Ii Receptor
Rat Adipose Cell
Di-Leucine Motif
Cytoplasmic Domain
Okadaic Acid
Plasma-Membrane
Intracellular Sequestration
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Queensland Brain Institute Publications
Institute for Molecular Bioscience - Publications
 
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